Gasification reactor

ABSTRACT

The invention is directed to a gasification reactor comprising a pressure shell, a reaction zone partly bounded by a vertically oriented tubular membrane wall, said wall being provided with one or more openings and wherein attached to the wall and above the opening a slag deflector is present. The invention is also directed to a process to prepare a mixture of hydrogen and carbon monoxide by gasification of a solid or liquid feedstock comprising between 15 and 50 wt % ash in a gasification reactor, wherein the feedstock and an oxygen containing gas and an optional moderator gas are provided to a burner as provided in an opening of the reactor and wherein the gasification in the reaction zone is carried out at a temperature in the range from 1200 to 1800° C. and at a pressure in the range from between 30 and 100 bar.

This application claims the benefit of European Application No. 07105317.7 filed Mar. 30, 2007 and U.S. Provisional Application No. 60/910,095 filed Apr. 4, 2007.

FIELD OF THE INVENTION

The invention is directed to a gasification reactor comprising a pressure shell and a reaction zone partly bounded by a vertically oriented tubular membrane wall. The membrane wall is provided with one or more openings.

BACKGROUND OF THE INVENTION

Such a gasification reactor is described in U.S. Pat. No. 4,202,672. This publication describes a coal gasification reactor provided with a pressure shell, a reaction zone and a membrane wall, which partly defines the reaction zone. The tubular shaped membrane wall comprises interconnected conduits in which evaporating cooling water is present.

In U.S. Pat. No. 4,959,080 a coal gasification process is described which may be performed in a gasification reactor as above. This publication described that a layer of slag will form on the membrane wall during gasification of coal. This layer of slag will flow downwards along the inner side of the membrane wall.

The Shell Coal Gasification Process also makes use of a gasification reactor comprising a pressure shell and a membrane walled reaction zone according to “Gasification” by Christofer Higman and Maarten van der Burgt, 2003, Elsevier Science, Burlington Mass., pages 118-120. According to this publication the Shell Coal Gasification Process is typically performed at 1500° C. and at a pressure of between 30 and 40 bar. The horizontal burners are placed in openings in the membrane wall.

Applicants have successfully performed the Shell Coal Gasification Process using different types of feedstock. However when processing feedstocks having a substantial high ash content, more in particular when processing such a feedstock at higher pressures, it is found that the operation of the process becomes more difficult due to ingress of slag into the openings in the membrane wall. Slag ingress may cause that the area forming the opening for the burner is damaged.

It would be advantageous to provide a gasification reactor, which is more suited to process feedstocks having a high ash content.

SUMMARY OF THE INVENTION

The invention provides a gasification reactor comprising a pressure shell, a reaction zone partly bounded by a vertically oriented tubular membrane wall, said wall being provided with one or more openings and wherein attached to the wall and above said opening a slag deflector is present.

Applicants have found that by having a slag deflector above the openings in the membrane wall less or even no slag ingress occurs resulting in less damage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a gasification reactor according to the invention.

FIG. 2 is a more detailed view of the reactor of FIG. 1 illustrating a burner opening in the membrane wall and represents the cross-sectional view CC′ of the same detail as shown in FIG. 3.

FIG. 3 is a more detailed view of the reactor of FIG. 1 illustrating a burner opening in the membrane wall.

FIGS. 3 a and 3 b are the cross-sectional views BB′ and AA′ respectively as shown in FIG. 3.

FIG. 4 shows more detailed view of the reactor of FIG. 1 illustrating a start-up burner opening in the membrane wall.

FIG. 4 a is the cross-sectional view DD′ of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

In a preferred embodiment, the present invention provides a slag deflector above one or more openings in a tubular membrane wall of a gasification reactor. The upper end of the slag deflector may be positioned between 0.1 and 3 times the width of the opening above the upper end of said opening. The slag deflector may be a rim attached to the membrane wall. The rim may be provided with a refractory coating. The deflector may be a conduit attached to the membrane wall provided with an inlet end for a cooling medium and an outlet end for used cooling medium. Said conduit may have a part located at a higher elevation above the opening and lower parts of the conduit extending side ways, such that in use at least part of the downwardly flowing slag is deflected away from the opening. The conduit may be provided with a refractory coating.

The slag deflector may be made from a low alloy steel with a Cr content up to 5 wt % or a high alloy steel with Cr content above 15 wt %.

Two or more deflectors may be positioned above the opening, wherein each deflector is vertically spaced away from the adjacent deflector. In a further embodiment two deflectors are positioned above the opening. The second deflector may be positioned between 0.5 and 3 times the width of the opening above the upper end of the first deflector. Such an embodiment having more than one deflector is especially suitable above the opening in the membrane wall in which a burner is provided. The deflector above such a burner opening may be designed such that part of the slag is directed away from the lower positioned opening and part of the slag retains it vertically downward flow path. This results that less slag comes near the opening but at the same time results in a sufficient flow of slag being maintained near said opening to provide the necessary isolation function.

In case the opening in the membrane wall concerns an opening for equipment, which will only be used during start-up, a more robust deflection of the slag is advantageous, because slag may accumulate during normal operation in such openings and solidify. Examples of equipment, which may be positioned in such openings during start-up, are a start-up burner, an igniter and means to detect a flame, e.g. a flame eye. In case the gasification reactor is required to be shut down and restarted for whatever reason, this hard slag needs to be removed mechanically from these openings and the start-up burner and its ignitor need to be disassembled for this purpose. This is found to be a time consuming operation, and it would therefore be advantageous to avoid it. Applicants have now found that by positioning a slag deflector above these openings, which deflect all the slag during normal operation, ingress and solidification of slag in said openings is avoided.

Other advantages and preferred embodiments will be discussed below making use of FIGS. 1-4.

FIG. 1 shows a gasification reactor having a vertically oriented tubular pressure shell 1, a membrane wall 3 and a reaction zone 2. Part 3 a of the membrane wall 3 is tubular shaped. The membrane wall 3 is composed of vertical conduits through which water flows. Water is supplied to the membrane wall via supply line 4 to a common distributor 5. The used cooling water, typically in the form of a water/steam mixture is discharged from the reactor via common header 6 and discharge line 7. The reactor is further provided with a quench gas supply 8. The invention is especially suited for a reactor, wherein the reaction zone 2 has an outlet 9 for a product gas at its upper end and a discharge outlet 10 for slag at its lower end. Product gas comprises a mixture of hydrogen and carbon monoxide as prepared in the gasification reactor. Two diametrically positioned openings 13 are shown in the membrane wall 3. In these openings 13, two diametrically placed burners 14 are placed. The reactor may comprise, for example, two or more pairs of such burners at the same elevation or alternatively at different elevations. Burner 14 is suited for performing the gasification of an ash containing solid or liquid carbonaceous feedstock. Suitable burners for a solid carbonaceous feedstock, suitably coal, are for example described in U.S. Pat. No. 4,523,529 and U.S. Pat. No. 4,510,874. The burners are fed by a coal supply line 11 and a supply line 12 for oxygen. Other openings, not shown in FIG. 1 for clarity reasons, may be provided in the membrane wall 3 for start-up burners, igniters and flame eyes. Above opening 13 a slag deflector 15 is shown.

FIG. 2 shows a detail of FIG. 1 showing opening 13 in the tubular part 3 a of the membrane wall 3. In this Figure two deflectors 15 a and 15 b for deflecting slag 19 are shown, spaced away from each other and above opening 13. In opening 13 a burner 14 is present, in which burner 14 and its flame the gasification reaction takes place. The opening 13 is further provided with a muffle 16. Muffle 16 comprises several vertically oriented, concentric and interconnected rings 17. Preferably at least 1 or more and more preferably all rings 17 are conduits having an inlet for a cooling medium via lines 20 and an outlet for used cooling medium via lines 22. The rings 17 are preferably made from a low alloy steel with a Cr content up to 5 wt % or a high alloy steel with Cr content above 15 wt %. The muffle 16 preferably extends some distance into the reaction zone 2 as shown to create a slag gutter 18 which allows the remaining slag 19 a as its flows towards the opening 13 to flow around the opening 13 and avoid ingress of the slag 19 a into opening 13.

FIG. 2 also shows a refractory coating 21 as present on the membrane wall 3 a. To keep the coating 21 fixed to said wall 3 a studs 23 are connected to wall 3 a.

Lines 20 are fluidly connected to cooling medium, typically water, distributor 24 and a common, typically water/steam mixture, header 25 respectively. The rings 17 are preferably welded together.

FIGS. 3, 3 a and 3 b shows a view of the reactor section of membrane wall 3 a shown in FIG. 2 as viewed from the centre of reaction zone 2. The reference numbers refer to the same elements. As shown deflector 15 a has an inlet 27 for a cooling medium and an outlet 26 for used cooling medium. Deflector 15 b is also provided with an inlet 29 for a cooling medium and an outlet 28 for used cooling medium. The deflectors 15 a and 15 b are provided with lower parts extending downwards making an angle α of between 90 and 140° when viewed in a horizontal direction, as shown in FIG. 3.

FIG. 4 shows a preferred slag deflector 30 for use above an opening for equipment, which will only be used during start-up as discussed above. In FIGS. 4 and 4 a a start-up burner 37 and an ignitor 36 are shown. Slag deflector 30 is made of two parallel conduits, 31 and 32 which extend more into the reaction zone 2 than the deflectors 15 a and 15 b of FIG. 2. This will result in that essentially all the slag 38 is deflected away from opening 33 during normal operation. Deflector 30 is provided with inlet 34 for a cooling medium and an outlet 35 for used cooling medium.

The cooling medium, preferably cooling water as supplied to the muffle 16 or to the above-illustrated deflector embodiments may be from the same source as the cooling water supplied to the membrane wall via 4. It can be also from a different source, which may have a lower water temperature and/or a different pressure.

Applicants found that the gasification reactor according to the invention is especially suited to prepare a mixture of carbon monoxide and hydrogen from a feedstock having an ash content of between 6 and 50 wt %. It has been found that the reactor according to the invention is especially suited for feeds having a high ash content, higher than 15 wt %, or even higher than 20 wt %. For economic reasons the ash content may be below 40 wt %. Feeds having an even higher ash content are preferably blended with lower ash content feeds in order to bring the total ash content of the combined feed to a value within the above ranges. Suited ash containing solid carbonaceous feeds are coal and biomass, for example wood and agricultural wastes. Suited ash containing liquid carbonaceous feeds are tar sand fractions and other bituminous oils. A particularly suited feedstock is coal having the ash contents as described above.

The gasification, or also referred to as partial oxidation, of the feedstock is carried out in the presence of an oxygen containing gas and possibly a moderator gas. A suited moderator gas is steam. Solid carbonaceous feedstocks may be provided to the burner as a mixture of solid particles in a carrier gas. Suited carrier gasses are nitrogen and carbon dioxide. The gasification in reaction zone 2 is carried out at a temperature in the range from 1200 to 1800° C. and at a pressure in the range from 1 to 200 bar, between 30 and 100 bar or at a pressure of above 35 bar and below 70 bar. 

1. A gasification reactor comprising a pressure shell, a reaction zone partly bounded by a vertically oriented tubular membrane wall, said wall being provided with one or more openings and wherein attached to the wall and above said opening a slag deflector is present.
 2. A gasification reactor according to claim 1, wherein the slag deflector is a conduit attached to the membrane wall provided with an inlet end for a cooling medium and an outlet end for used cooling medium and wherein said conduit has a part located at a higher elevation above the opening and lower parts of the conduit extending side ways, such that in use at least part of the downwardly flowing slag is deflected away from the opening.
 3. A gasification reactor according to claim 1, wherein 2 or more deflectors are positioned above the opening and wherein each deflector is vertically spaced away from the adjacent deflector.
 4. A gasification reactor according to claim 2, wherein the deflector comprises parts extending downwards to make an angle of between 90 and 140°.
 5. A gasification reactor according to claim 1, wherein in the opening a start-up burner and or an ignitor is present.
 6. A gasification reactor according to claim 1, wherein in the opening a flame detector is present.
 7. A gasification reactor according to claim 1, wherein in the opening a burner is present for performing the gasification of an ash containing solid or liquid carbonaceous feedstock.
 8. A gasification reactor according to claim 7, wherein the burner is positioned in the opening via a burner muffle.
 9. A gasification reactor according to claim 1, wherein the deflector is made from a low alloy steel with a Cr content of up to 5 wt % or a high alloy steel with a Cr content above 15 wt %.
 10. A gasification reactor according to claim 1, wherein the reaction zone has an outlet for a product gas at its upper end and an outlet for slag at its lower end.
 11. A process to prepare a mixture of hydrogen and carbon monoxide by gasification of a solid or liquid feedstock comprising between 15 and 50 wt % ash in a gasification reactor according to claim 1, wherein the feedstock and an oxygen containing gas and an optional moderator gas are provided to a burner as provided in an opening of the reactor and wherein the gasification in reaction zone is carried out at a temperature in the range from 1200 to 1800° C. and at a pressure in the range from between 30 and 100 bar. 